what is this language??

I heard of this I think... does it have to do with cell phones? if so why does it have to have a seperate lang for itself? also where can I find some basic tutorials on it? does anybody know if they are compatible with all cell phones all over the world?? thanx alot

As for compatabilty it is much better than standards compliance on the web, but with new technologies it's starting to get tricky again Older devices can only understand HDML, ignore them like you would NN users